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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        let chior = [];  //合唱团
        let duck = {
            duckSinging: function(){
                console.log('嘎嘎嘎');
            }
        }
        //999
        for(let i = 0; i<999 ;i++){
            if (checkIsDuck(duck)){
            chior.push(duck)
            }
        }

        let chick = {
            // 只要有两条腿,并且嘎嘎嘎叫就是鸭子
            duckSinging:function(){
                console.log('嘎嘎嘎');
            }

        }
        if (checkIsDuck(duck)){
            chior.push(chick);
        }
        chior.push(chick);
        /*
        *@func 校验是否是只鸭子
        *@params obj {}
        *@return boolean
        */
        function checkIsDuck(obj) {
            if(obj.hasOwnProperty('duckSingsing') && typeof chick.duckSinging == 'function'){
                return true;
            }
            return false;
        }

        if(chior.length >= 1000){
            console.log('招募工作已完成')
        }
    </script>
</body>
</html>